There have been numerous Air Cushion Vehicle (ACV) designs with the majority using either full or partial periphery flexible fabric air seals. The full periphery flexible seal craft are normally known as Ground Effect Machines (GEMs) and are amphibious. The second common type generally use fixed structure catamaran side keels with flexible seals fore and aft to thereby define a single rectangular air cushion that supports a craft limited to the marine environment. These latter craft are generally referred to as Surface Effect Ships (SESs).
Some simpler and yet vastly improved SES variations have been proposed by the inventor such as can be seen in Burg, U.S. Pat. Nos. 5,176,095 and 5,415,120. All of these utilize multi-hull designs that have a simple hull structure recess built into one or more of the multi-hulls. There are no air cushions between the multiple hulls and there are no flexible seals. Quite simply, these inventions avoid the problems associated with flexible seal SESs including high flexible seal initial and maintenance costs, a rough bumpy ride related to the flexible bow seal of the generic flexible seal SES allowing waves to disturb the large air cushion that is in reality a large gas spring, and poor ride qualities in rough seas that is largely due to the wide barn door shape of the SES's bow seal.
The instant invention presents improvements to ideas presented in Inventor's previously listed patents in that it provides an exceptionally smooth ride in rough seas when at rest or traveling at low speeds. This is done without sacrificing the high speed efficiency of the Inventor's previous inventions. The ability to have a very efficient high speed vessel combined with exceptional stability when at rest or low speeds offers unique advantage. Some applications for this new technology include military craft, offshore oil field support vessels, fishing vessels, offshore gaming vessels, and other craft. It is primarily applicable to any marine craft that must be able to get to a station location quickly at high speed and then stay on station for long periods with a minimum of passenger and crew discomfort.
A very stable relatively low speed vessel has been available for a number of years in the form of the Small WAterplane Twin Hull (SWATH). The SWATH concept generally uses twin submerged torpedo or submarine shaped hulls disposed in catamaran configuration below a main hull that is above the waterline. Each submerged torpedo hull is connected to the main hull by one or more struts. While very stable, SWATH has a high drag coefficient at higher speeds. For example, a 100 foot SWATH would generally be considered to require very high propulsive power at over 20 knots. This is due to the very large amount of wetted surface area of the twin submerged sidehulls. Further, since the SWATH's sidehulls are submerged its overall draft requirements are considered excessive for all but deep water ports and cruising areas.
The instant invention, in its preferred embodiment, offers three distinct modes of operation: 1) High speed as a minimum draft Surface Effect Ship wherein blower pressurized air cushions built into at least one of the multiple hulls support a majority of displacement, 2) Intermediate speed where the blower system is turned off and the hulls function primarily in a planing and/or displacement mode, and 3) Low speed maximum stability configuration wherein the sidehulls are at least semi-submerged, generally with the assistance of water ballast, such that there is a minimum strut waterplane area which results in minimum craft motions in a seaway.
The instant invention offers advancements over applicant's earlier inventions as well as over the prior art. These advancements are discussed in some detail in the following sections.